package com.data.basic.chapter03;

/**
 * 循环队列
 */
public class LoopQueue<E> implements Queue<E> {
    private E [] data;
    private int front,tail;
    private int size;

    public LoopQueue(int capacity) {
        // 队头和队尾需要空一格来进行
        data = (E[]) new Object[capacity+1];
        front =0;
        tail=0;
        size=0;
    }

    public LoopQueue(){
        this(10);
    }
    public int getCapacity(){
       return data.length-1;
    }

    public void enqueue(E e) {
        if ((tail+1)%data.length==front){
            resize(getCapacity()<<1);
        }
        data[tail]  = e;
        tail = (tail+1)%data.length;
        size++;


    }

    private void resize(int newCapacity) {
        E[] newData = (E[]) new Object[newCapacity+1];
        for (int i=0;i<size;i++){
             newData[i]=data[(front+i)%data.length];
        }
        data =newData;
        front=0;
        tail = size;
    }




    public E dequeue() {
        if (isEmpty()){
            throw new IllegalArgumentException(" Cannont dequeue from a empty queue");
        }
        E ret = data[front];
        data[front]=null;
        front = (front+1)%data.length;
        size--;
        if (size==getCapacity()/4&&getCapacity()/2!=0){//缩小容量,但是默认容量不会缩

            resize(getCapacity()/2);
        }
        return ret;
    }

    public E getFront() {
        if(isEmpty()){
            throw new IllegalArgumentException("Queue is empty");
        }
        return data[front];
    }

    public int getSize() {
        return size;
    }

    public boolean isEmpty() {
        return front==tail;
    }

    @Override
    public String toString() {
        StringBuilder res = new StringBuilder();
        res.append(String.format("Queue：size= %d,capacity= %d\n",size,getCapacity()));
        res.append("front:[");
        for (int i=front;i!=tail;i=(i+1)%data.length){// 队列遍历
            res.append(data[i]);
            if ((i+1)%data.length!=tail)
                res.append(",");
        }
        res.append("]tail");
        return res.toString();
    }

    public static void main(String[] args) {
        LoopQueue<Integer> loopQueue = new LoopQueue<Integer>();
        for (int i =0;i<15;i++){
            loopQueue.enqueue(i);
            System.out.println(loopQueue);
            if (i%3==2){
                loopQueue.dequeue();
            }

            }
        System.out.println(loopQueue);
    }
}
